Eeprom array with well contacts

ABSTRACT

A semiconductor integrated circuit device includes a cell well, a memory cell array formed on the cell well and having a memory cell area and cell well contact area, first wiring bodies arranged in the memory cell area, and second wiring bodies arranged in the cell well contact area. The layout pattern of the second wiring bodies is the same as the layout pattern of the first wiring bodies. The cell well contact area comprises cell well contacts that have the same dopant type as the cell well and that function as source/drain regions of dummy transistors formed in the cell well contact area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. application Ser. No. 11/567,805, filed onDec. 7, 2006, which is a Continuation Application of PCT Application No.PCT/JP2005/017206, filed Sep. 12, 2005, which was published under PCTArticle 21(2) in English.

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2005-100955, filed Mar. 31, 2005,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor integrated circuit device andmore particularly to a semiconductor integrated circuit device having anonvolatile semiconductor memory.

2. Description of the Related Art

EEPROMs are known as semiconductor memories, for example, nonvolatilesemiconductor memories. Some EEPROMs have wells whose potential can bechanged and memory cell transistors formed on the wells. As arepresentative example thereof, a flash memory, for example, a NANDflash memory in which data in a plurality of memory cell transistors aresimultaneously erased is provided.

Each memory cell transistor of the NAND flash memory has a chargestorage layer, for example, a floating gate. The level of the thresholdvoltage of the memory cell transistor varies according to the amount ofcharge stored in the floating gate. Data is set and stored according tothe level of the threshold voltage.

When data is erased in the NAND flash memory, positive potential isapplied to a well called a cell well. Further, when data is written orread out, the potential of the cell well is set to zero, for example.

Thus, the potential of the cell well of the NAND flash memory is changedaccording to the operation thereof. Therefore, the cell well isconnected to a cell well bias circuit which applies the potentialcorresponding to the operation to the cell well. The potential generatedfrom the cell well bias circuit is supplied to a memory cell array via acell well bias line and applied to the cell well via a cell wellcontact. Some cell well lines are laid out parallel to bit lines in thememory cell array, for example, and some cell well contacts are arrangedunder the cell well bias lines in the memory cell array.

Wiring bodies such as the bit lines, word lines, block selection linesand floating gates are laid out in a repetitive form in the memory cellarray. However, the repetitive arrangement cannot be maintained in theportions of the cell well bias lines and cell well contacts. A NANDflash memory having a layout pattern in which the repetitive arrangementis partially lost is described in Jpn. Pat. Appln. KOKAI Publication No.2000-91546.

BRIEF SUMMARY OF THE INVENTION

A semiconductor integrated circuit device according to a first aspect ofthe present invention comprises a cell well, a memory cell array formedon the cell well and having a memory cell area and cell well contactarea, first wiring bodies arranged in the memory cell area, and secondwiring bodies arranged in the cell well contact area, the layout patternof the first wiring bodies being the same as the layout pattern of thesecond wiring bodies.

A semiconductor integrated circuit device according to a second aspectof the present invention comprises a cell well, first wirings, secondwirings which intersect with the first wirings, third wirings arrangedparallel to the second wirings, transistors arranged at intersectionsbetween the first and second wirings and each having the cell well as abackgate thereof, dummy transistors arranged at intersections betweenthe first and third wirings and each having the cell well as a backgatethereof, one of source and drain portions thereof being set to have thesame conductivity type as that of the cell well, first contactsrespectively connected to the second wirings and corresponding ones ofthe source and drain portions of the transistors, and second contactsrespectively connected to the third wirings and corresponding ones ofthe source and drain portions of the dummy transistors. A semiconductorintegrated circuit device according to a third aspect of the presentinvention comprises a cell well, a first wiring, a plurality of secondwirings which intersect with the first wiring, a plurality of thirdwirings arranged parallel to the second wirings, a plurality of firsttransistors arranged at intersections between the first wiring and theplurality of second wirings and having the cell well as backgatesthereof, a plurality of dummy transistors arranged at intersectionsbetween the first wirings and the plurality of third wirings and havingthe cell well as backgates thereof, one of source and drain portionsthereof being set to have the same conductivity type as that of the cellwell, a plurality of first contacts respectively connected to theplurality of second wirings and to corresponding ones of the source anddrain portions of the plurality of transistors, and a plurality ofsecond contacts respectively connected to the plurality of third wiringsand to corresponding ones of the source and drain portions of theplurality of dummy transistors.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a plan view showing an example of the layout of asemiconductor integrated circuit device according to one embodiment ofthis invention;

FIG. 2 is a circuit diagram showing a circuit example of a memory cellarray 3 shown in FIG. 1;

FIG. 3 is a plan view showing an example of a gate layout pattern of thememory cell array 3 shown in FIG. 1;

FIG. 4 is a plan view showing an example of a first-layered metal layoutpattern of the memory cell array 3 shown in FIG. 1;

FIG. 5 is a plan view showing an example of a second-layered metallayout pattern of the memory cell array 3 shown in FIG. 1;

FIG. 6 is a cross-sectional view taken along the 6-6 line in FIGS. 3 to5;

FIG. 7 is a cross-sectional view taken along the 7-7 line in FIGS. 3 to5;

FIG. 8 is a cross-sectional view taken along the 8-8 line in FIGS. 3 to5;

FIG. 9A is a plan view showing a memory cell array of a semiconductorintegrated circuit device according to the embodiment of this invention;

FIG. 9B is a diagram showing an average transmission light amount of aphotomask;

FIG. 10A is a plan view showing a memory cell array of a semiconductorintegrated circuit device according to a reference example of thisinvention;

FIG. 10B is a diagram showing an average transmission light amount of aphotomask;

FIG. 11 is a view showing an advantage attained in the embodiment ofthis invention;

FIG. 12 is a view showing an advantage attained in the embodiment ofthis invention;

FIG. 13 is a cross-sectional view showing a semiconductor integratedcircuit device according to a modification of the embodiment; and

FIG. 14 is a cross-sectional view showing a semiconductor integratedcircuit device according to another modification of the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

One of the important factors when a semiconductor integrated circuitdevice is miniaturized is the lithography technology. It becomespossible to transfer a fine pattern onto the semiconductor integratedcircuit device by enhancing the resolution of the lithographytechnology. In order to enhance the resolution, it is important to paymuch attention to the lithography technology itself, for example, thecondition of illumination and formation of a photomask.

Further, it is also important to pay much attention to the semiconductorintegrated circuit device itself by providing a layout pattern which canbe easily resolved. For example, if the repetitive arrangement of bitlines and word lines is lost and the repetitive arrangement of blockselection lines, cell source lines and floating gate layers is lost whenthey are used, a problem which obstructs the development of the finepatterning technique may occur. The present embodiment relates to thetechnique for improving the semiconductor integrated circuit deviceitself.

There will now be described one embodiment of this invention withreference to the accompanying drawings. In this explanation, commonreference symbols are attached to like portions throughout the drawings.

FIG. 1 is a plan view showing an example of the layout of asemiconductor integrated circuit device according to one embodiment ofthis invention. In this example, a semiconductor memory such as a NANDflash memory is shown as one example of a semiconductor integratedcircuit device.

As shown in FIG. 1, a main cell array 3, row decoders 5, page buffer 7and peripheral circuit 9 are mainly arranged on a semiconductor chip 1.

Memory cell transistors are arranged in a matrix form in the memory cellarray 3. The row decoder 5 selects a row of the memory cell array 3according to an address signal. The page buffer 7 holds write data ofone page supplied from the exterior, for example, at the write operationtime and supplies the thus held write data to a selected page of thememory cell array 3. Further, it holds read data of one page read fromthe memory cell array 3 at the read operation time and supplies the thusheld readout data to the exterior, for example. In the peripheralcircuit 9, memory peripheral circuits such as a command decoder, boostercircuit and cell well bias circuit are arranged.

The memory cell array 3 of this example is formed on a cell well, forexample, P-type cell well (CELL P-WELL). In the memory cell array 3,memory cell areas 11 and cell well contact areas 13 are set. A pluralityof memory cell areas 11 and a plurality of cell well contact areas 13are alternately arranged, for example.

(Circuit Example)

FIG. 2 is a circuit diagram showing a circuit example of the memory cellarray 3 shown in FIG. 1.

As shown in FIG. 2, memory cell transistors MT, source-side blockselection transistors STS and drain-side block selection transistors STDare arranged in the memory cell area 11. The transistors MT, STS, STDare formed on the cell well (CELL P-WELL) and the backgates thereof areconnected to the cell well (CELL P-WELL).

Further, in the cell well contact area 13, dummy memory cell transistorsDMT, dummy source-side block selection transistors DSTS and dummydrain-side block selection transistors DSTD are arranged. The dummytransistors DMT, DSTS, DSTD are formed on the cell well (CELL P-WELL)and the backgates thereof are connected to the cell well (CELL P-WELL)like the transistors MT, STS, STD. The structure of the dummytransistors DMT, DSTS is the same as that of the transistors MT, STS.Further, the structure of the dummy transistor DSTD is similar to thatof the transistor STD except that the conductivity type of one of thesource and drain portions is the same as that of the cell well (CELLP-WELL). The dummy transistors DMT, DSTD, DSTS are not used as thememory cells and block selection transistors.

Bit lines BL are arranged in the column direction in the memory cellarea 11 and connected to corresponding ones of the source and drainportions of the transistors STD.

A cell well bias line CPWELL is arranged parallel to the bit lines BL inthe cell well contact area and connected to the cell well (CELL P-WELL).In this example, the bias line is connected to the cell well (CELLP-WELL) via one of the source and drain portions of the dummy transistorDSTD. The conductivity type of one of the source and drain portions ofthe dummy transistor DSTD is the same as that of the cell well (CELLP-WELL). In this example, for example, it is of a P type. The cell wellbias line CPWELL is a wiring which applies bias potential to the cellwell (CELL P-WELL). The bias potential is generated from the cell wellbias circuit. The cell well (CELL P-WELL) is biased to low potential(for example, 0V) via the cell well bias line CPWELL at the readoutoperation time and write operation time. Further, at the erase operationtime, it is biased to high potential (for example, 20V) via the cellwell bias line CPWELL.

Cell source lines SRC are arranged in the row direction to cross thememory cell areas 11 and cell well contact areas 13. The columndirection is a direction which intersects with the row direction and,for example, the column direction intersects with the row direction atright angles. The cell source line SRC is connected to one of the sourceand drain portions of the transistors STS and one of the source anddrain portions of the dummy transistors DSTS.

The transistors MT are serially connected between the other one of thesource and drain portions of the transistor STD and the other one of thesource and drain portions of the transistor STS. Likewise, the dummytransistors DMT are serially connected between the other one of thesource and drain portions of the dummy transistor DSTD and the other oneof the source and drain portions of the dummy transistor DSTS.

The control gates of the transistors MT and the control gates of thedummy transistors DMT which are arranged on the same row are commonlyconnected and function as a word line WL.

Likewise, the gates of the transistors STS and the gates of the dummytransistors DSTS which are arranged on the same row are commonlyconnected and function as a source-side block selection line SGS.

Also, the gates of the transistors STD and the gates of the dummytransistors DSTD which are arranged on the same row are commonlyconnected and function as a drain-side block selection line SGS.

(Example of Structure)

FIGS. 3 to 5 plan views each showing an example of the structure of thememory cell array 3 shown in FIG. 1. FIG. 3 shows an example of a gatelayout pattern, FIG. 4 shows an example of a first-layered metal (M0)layout pattern and FIG. 5 shows an example of a second-layered metal(M1) layout pattern. Further, FIG. 6 is a cross-sectional view takenalong the 6-6 line in FIGS. 3 to 5, FIG. 7 is a cross sectional viewtaken along the 7-7 line in FIGS. 3 to 5 and FIG. 8 is a cross sectionalview taken along the 8-8 line in FIGS. 3 to 5.

As shown in FIGS. 3 to 8, for example, an N-type cell well (CELL N-WELL)33 and P-type cell well (CELL P-WELL) 35 are formed in a P-typesemiconductor substrate (P-SUBSTRATE) such as a P-type silicon substrate1. The cell well 33 electrically isolates the cell well 35 from thesubstrate 1.

In the surface area of the substrate 1 (in the surface area of the cellwell 35 in FIGS. 3 to 8), element isolation insulating films 37 areformed. One example of the element isolation insulating film 37 is ashallow trench isolation (STI) region. The element isolation insulatingfilms 37 isolate active regions AA in the surface region of thesubstrate 1 (in the surface area of the cell well 35 in FIGS. 3 to 8).In this example, the layout pattern of the active regions AA of thememory cell area 11 is the same as the layout pattern of the activeregions AA of the cell well contact area 13.

On each of the active regions AA, a gate insulating film 39 is formed.One example of the gate insulating film 39 is a silicon dioxide film. Oneach gate insulating film 39, a floating gate (FG) 41 is formed. Oneexample of the floating gate is a conductive polysilicon film. On eachfloating gate 41, a gate-gate insulating film 43 is formed. One exampleof the gate-gate insulating film 43 is a three-layered film (ONO film)of a silicon nitride film/silicon dioxide film/silicon nitride film. Oneach gate-gate insulating film 43, a control gate 45 is formed.

One example of the control gate 45 is a laminated film (polycide film)of a conductive polysilicon film and metal silicide film.

The gate electrode of each of the memory cell transistors MT and dummymemory cell transistors DMT has a laminated structure of the floatinggate 41, gate-gate insulating film 43 and control gate 45. Each controlgate 45 is commonly used by the transistors MT and dummy transistors DMTarranged in the row direction and functions as the word line WL.

The gate electrode of each of the block selection transistors STD (orSTS) and dummy block selection transistors DSTD (or DSTS) has alaminated structure of a conductive film 41′ which is the same as thefloating gate 41, an insulating film 43′ which is the same as thegate-gate insulating film 43 and a conductive film 45′ which is the sameas the control gate 45. The insulating film 43′ of this example has anopening 47 and the conductive film 45′ is electrically connected to theconductive film 41′ via the opening 47. In this example, the conductivefilms 41′ and 45′ are commonly used by the transistors STD (or STS) anddummy transistors DSTD (or DSTS) which are arranged in the row directionand function as drain-side block selection lines SGD (or source-sideblock selection lines SGS).

Thus, in this example, the layout pattern of the gates arranged in thememory cell area 11 is the same as the layout pattern of the gatesarranged in the cell well contact area 13.

N-type source/drain diffusion layers 49 are formed in portions of theactive regions AA which lie under between the gate electrodes of thetransistors MT. Further, N-type source/drain diffusion layers 49 arealso formed in portions of the active regions AA which lie under betweenthe gate electrodes of the transistors MT and the gate electrodes of thetransistors STD (or STS), between the gate electrodes of the dummytransistors DMT and between the gate electrodes of the dummy transistorsDMT and the gate electrodes of the dummy transistors DSTD (or DSTS).

N-type source/drain diffusion layers 49′ are formed in portions of theactive regions AA which lie under between the gate electrodes of thetransistors STD.

Further, P-type diffusion layers 50 having the same conductivity type asthe cell well 35 are formed in portions of the active regions AA whichlie under between the gate electrodes of the dummy transistors DSTD.

In addition, N-type source/drain diffusion layers 49″ are formed inportions of the active regions AA which lie under between the gateelectrodes of the transistors STS and between the gate electrodes of thedummy transistors DSTS.

The N-type source/drain diffusion layers 49′ and P-type diffusion layers50 are connected to respective plugs 51. Further, the N-typesource/drain diffusion layers 49″ are connected to respective plugs 52.One example of the plugs 51, 52 is a metal film. As an example of themetal film, a titanium film and tungsten film are used. In this example,the layout pattern of the plugs 51, 52 arranged in the memory cell area11 is the same as the layout pattern of the plugs 51, 52 arranged in thecell well contact area 13.

The plugs 51 are connected to respective local internal wirings 53. Oneexample of the local internal wiring 53 is a metal film. As an exampleof the metal film, an aluminum film and copper film are used.

The plugs 52 are connected to respective cell source lines SRC. Oneexample of the cell source line SRC is a metal film. As an example ofthe metal film, an aluminum film and copper film are used. In thisexample, the cell source line SRC is formed on the same plane as thelocal internal wiring 53. For example, these wirings are formed by useof the same conductive film, for example, a first-layered metal (M0).Further, in this example, the layout pattern of the first-layered metal(M0) arranged in the memory cell area 11 is the same as the layoutpattern of the first-layered metal (M0) arranged in the cell wellcontact area.

The local internal wirings 53 are connected to respective plugs 55. Inthis example, the layout pattern of the plugs 55 arranged in the memorycell area 11 is the same as the layout pattern of the plugs 55 arrangedin the cell well contact area 13.

The plugs 55 arranged in the memory cell area 11 are connected to thebit line BL. The plugs 55 arranged in the cell well contact area 13 areconnected to the cell well bias line CPWELL. In this example, the bitline BL and cell well bias line CPWELL are formed by use of the sameconductive film, for example, a second-layered metal (M1). Further, inthis example, as shown in FIG. 8, the width of the bit line BL in therow direction is the same as the width W of the cell well bias lineCPWELL in the row direction. Further, the arrangement pitch of the bitlines BL is the same as the arrangement pitch P of the cell well biaslines CPWELL. That is, in this example, the layout pattern of the bitlines BL is the same as the layout pattern of the cell well bias linesCPWELL.

In the semiconductor integrated circuit device according to the presentembodiment of this invention, the layout pattern of the physicalstructure arranged in the memory cell array 3 is the same in the memorycell area 11 and in the cell well contact area 13. Therefore, therepetitive form of the physical structure can be maintained in the cellwell contact area 13 and the repetitive form thereof can be constantlyattained in the entire portion of the memory cell array 3. For example,the physical structure includes the bit lines BL, word lines WL, blockselection lines SGS, SGD and cell well bias lines CPWELL in the case ofNAND flash memory.

One advantage of the semiconductor integrated circuit device accordingto the present embodiment of this invention is explained with referenceto FIGS. 9 and 10.

One of the advantages is that the dummy area can be reduced oreliminated in the memory cell array 3.

FIG. 9A is a plan view showing the memory cell array of thesemiconductor integrated circuit device according to the embodiment ofthis invention and showing a layout pattern of bit lines and cell wellbias lines. FIG. 10A is a plan view showing a memory cell array of asemiconductor integrated circuit device according to a reference exampleof this invention and showing a layout pattern of bit lines and cellwell bias lines.

As shown in FIG. 9A, according to the present embodiment, the layoutpattern of the bit lines BL and cell well bias lines CPWELL is the samein the memory cell area 11 and in the cell well contact area 13.Therefore, the repetitive form of the layout pattern of the bit lines BLand cell well bias lines CPWELL is constant in the entire portion of thememory cell array 3.

On the other hand, as shown in FIG. 10A, in the reference example, forexample, in a device disclosed in Jpn. Pat. Appln. KOKAI Publication No.2000-91546, the repetitive form of the layout pattern of the bit linesBL and cell well bias lines CPWELL cannot be maintained in the cell wellcontact area 13 since the width of the cell well bias line CPWELL islarger than the width of the bit line BL.

The above problem makes it difficult to uniformly subject the bit linesBL to a lithography process. One of the reasons is that the ratio of thelight transmission portion/light shielding portion becomes different ina cell well bias line pattern portion A and in a bit line patternportion B of a photomask 100 as shown in FIG. 10A. The width of the cellwell bias line pattern is large and the light shielding portion islarger. Therefore, the light shielding portion is dense. On the otherhand, the width of the bit line pattern is small and the light shieldingportion is less. Therefore, the light shielding portion is coarse. Thedifference in the density causes a difference Δ0 between the averageamount of transmission light which passes through the portion A and theaverage amount of transmission light which passes through the portion B.Due to the difference Δ0, a portion C in which the average transmissionlight amount is changed occurs between the portions A and B. In theportion C, not the cell well bias line pattern but the bit line patternis formed as in the portion B. However, since the average amount oftransmission light which passes through the portion C and theneighboring portion thereof is different from the average amount oftransmission light which passes through the portion B and theneighboring portion thereof, the widths of the bit liens BL formed aredifferent. For example, since the bit line capacitances are different ifthe widths of the bit lines BL are different, a variation in the readspeed and write speed between the bit lines becomes larger in thesemiconductor memory. This lowers the performance of the semiconductormemory. Therefore, it is common practice to form the bit line pattern inthe portion C and set the portion as an area (dummy area) 15 which isnot used as a memory in the actual device as shown in FIG. 10A.

On the other hand, according to the present embodiment, the width of thecell well bias line CPWELL is the same as that of the bit line BL andthe arrangement pitches thereof are constant. Therefore, as shown inFIG. 9B, the ratio of the light transmission portion/light shieldingportion becomes constant in the cell well bias line pattern portion Aand in the bit line pattern portion B of the photomask 100. As a result,the average transmission light amount through the portion A becomes thesame as the average transmission light amount through the portion B andthe portion C in which the average transmission light amount varies asshown in the reference example does not occur. Therefore, the dummy area15 can be reduced or eliminated in the memory cell array 3.

Thus, if the dummy area 15 can be reduced or eliminated, an advantagethat the area of the memory cell array 3 can be reduced can be attainedin a case where the memory capacity is kept constant as shown in FIG.11.

Further, as shown in FIG. 12, in a case where the area of the memorycell array 3 is kept constant, an advantage that the memory capacity canbe increased since the memory cell area 11 can be increased can beattained.

Therefore, according to the present embodiment, a semiconductor memoryin which the memory cell array 3 can be easily miniaturized and can beintegrated with high integration density can be provided.

When it is desired to increase the capacity of the cell well bias lineCPWELL or lower the resistance thereof, the cell well bias circuit maybe connected to a plurality of cell well bias lines as in the presentembodiment. For example, in the present embodiment, the cell well biascircuit is connected to two cell well bias lines CPWELL for each cellwell contact area 13.

Next, some of the devices which maintain the repetitive form in thesemiconductor integrated circuit device according to the embodiment ofthis invention.

(Cell Well Contact)

In the present embodiment, dummy transistors for cell well contacts areprovided below the cell well bias lines CPWELL. The contact dummytransistor has a P-type source/drain portion 50 having the sameconductivity type as a P-type cell well 35. In the present embodiment,the contact dummy transistor is the dummy block selection transistorDSTD shown in FIG. 7. A connection (cell well contact) between the cellwell bias line CPWELL and the cell well 35 is made via the P-typesource/drain portion 50.

Thus, it is not necessary to form a particular pattern in the cell wellcontact as shown in the reference example of FIG. 10A, for example, byutilizing the source/drain portion of the transistor.

Therefore, the gate layout pattern of the cell well contact area 13 canbe set to the same as the gate layout pattern of the memory cell area11.

For example, the P-type source/drain portion 50 can be formed asfollows.

First, like the other transistors, an N-type source/drain portion isformed in the source/drain portion of the contact dummy transistor.After this, for example, P-type impurity is doped into the source/drainportion of the contact dummy transistor to change the conductivity typeof the N-type source/drain portion to a P conductivity type.

Further, in the present embodiment, transistors are provided below thebit lines. The transistor has an N-type source/drain portion 49′ havinga conductivity type different from that of the P-type cell well 35. Inthe present embodiment, the transistor is the block selection transistorSTD shown in FIG. 6.

The bit line BL is connected to the N-type source/drain portion 49′ ofthe transistor via a connection member. In the present embodiment, theconnection member is the plug 51. The cell well bias line is connectedto the P-type source/drain portion 50 of the contact dummy transistorvia a connection member. In the present embodiment, the connectionmember is the plug 51. In the present embodiment, the plugs 51 arealigned in the row direction as shown in FIG. 3.

Thus, if the plugs 51 are aligned in the row direction, the layoutpattern of the plugs 51 of the cell well contact area 13 can be formedas the same pattern as the layout pattern of the plugs 51 of the memorycell area 11.

Conventionally, doped polysilicon, for example, N-type doped polysiliconhaving the same conductivity type as the N-type source/drain portion 49′may be used to form the plug 51 in some cases. However, in the presentembodiment, the N-type portion 49′ and P-type portion 50 are provided inthe source/drain portion. Therefore, if doped polysilicon is used toform the plug 51, PN junction may be made between the plug 51 and thesource/drain portion in some cases. In order to prevent formation of thePN junction, for example, metal may be used to form the plug 51 asdescribed before. One example of the metal is titanium or tungsten asdescribed before.

(Block Selection Line)

Generally, the block selection line is shunted by use of anotherconductive layer in order to lower the resistance thereof. For thispurpose, it becomes necessary to provide a block selection contact areain which the other conductive layer is connected to the block selectionline. Due to the presence of the contact area, the repetitive form ofthe layout pattern in the memory cell array 3 cannot be maintained.

In the present embodiment, there is no block selection line contactarea. Instead of this, for example, a conductive film 45′ formed by useof the same conductive material as the control gate 45 is connected to aconductive layer 41′ formed by use of the same material as the chargestorage layer 41 (FG). As shown in FIGS. 6 and 7, the connection is madeby use of an opening 47 formed in the conductive layer 43′.

Thus, the resistance of the block selection line can be lowered byconnecting the conductive film 45′ to the conductive layer 41′. In thiscase, it is not necessary to provide the block selection line contactarea in the memory cell array 3 by making the connection by use of theopening 47 formed in the insulating film 43′.

Thus, according to this embodiment, when an attempt is made to lower theresistance of the block selection line, the repetitive arrangement ofthe layout pattern of the memory cell array 3 can be maintained.

As shown in FIGS. 13 and 14, the connection between the conductive layer41′ and the conductive film 45′ can be attained by eliminating theinsulating film 43′ and setting the upper surface of the conductivelayer 41′ in contact with the undersurface of the conductive film 45′without forming the opening 47. FIG. 13 corresponds to thecross-sectional view of FIG. 6 and FIG. 14 corresponds to thecross-sectional view of FIG. 7.

This invention is explained by use of the embodiment, but this inventionis not limited to the above embodiment and can be variously modifiedwithout departing from the technical scope thereof when this inventionis embodied. Further, the above embodiment of this invention is not onlyone embodiment.

In the above embodiment, various stages of this invention are containedand inventions of various stages can be extracted by adequatelycombining a plurality of constituents disclosed in the respectiveembodiments.

In the above embodiment, this invention is explained by use of theexample in which this invention is applied to the semiconductorintegrated circuit device, for example, semiconductor memory, but asemiconductor integrated circuit device such as a processor or systemLSI containing a semiconductor memory is contained in the scope of thisinvention.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A semiconductor integrated circuit device comprising: a cell well,first wirings, second wirings which intersect with the first wirings,third wirings arranged parallel to the second wirings, transistorsarranged at intersections between the first wirings and the secondwirings and having the cell well as backgates thereof, dummy transistorsarranged at intersections between the first wirings and the thirdwirings and having the cell well as backgates thereof, one of source anddrain portions thereof being set to have the same conductivity type asthat of the cell well, first contacts respectively connected to thesecond wiring and to corresponding ones of the source and drain portionsof the transistors, and second contacts respectively connected to thethird wiring and to corresponding ones of the source and drain portionsof the dummy transistors.
 2. The device according to claim 1, whereinthe first and second contacts are formed of metal.
 3. The deviceaccording to claim 1, wherein the first and second contacts are alignedin the row direction.
 4. The device according to claim 1, wherein thefirst wirings are word lines, the second wirings are bit lines and thethird wirings are cell well bias lines.
 5. The device according to claim4, wherein the transistor which is arranged adjacent to the bit line andcell well bias line, connected to the bit line and having the word lineas a gate thereof is a memory cell transistor.
 6. The device accordingto claim 1, wherein the first wirings are block selection lines, thesecond wirings are bit lines and the third wirings are cell well biaslines.
 7. The device according to claim 6, wherein the transistor whichis arranged adjacent to the bit line and cell well bias line, connectedto the bit line and having the block selection line as a gate thereof isa block selection transistor.
 8. A semiconductor integrated circuitdevice comprising: a cell well, a first wiring, a plurality of secondwirings which intersect with the first wiring, a plurality of thirdwirings arranged parallel to the second wirings, a plurality of firsttransistors arranged at intersections between the first wiring and theplurality of second wirings and having the cell well as backgatesthereof, a plurality of dummy transistors arranged at intersectionsbetween the first wiring and the plurality of third wirings and havingthe cell well as backgates thereof, one of source and drain portionsthereof being set to have the same conductivity type as that of the cellwell, a plurality of first contacts respectively connected to theplurality of second wirings and to corresponding ones of the source anddrain portions of the plurality of transistors, and a plurality ofsecond contacts respectively connected to the plurality of third wiringsand to corresponding ones of the source and drain portions of theplurality of dummy transistors.
 9. The device according to claim 8,wherein the first and second contacts are formed of metal.
 10. Thedevice according to claim 8, wherein the first wiring is a word line,the plurality of second wirings are bit lines and the plurality of thirdwirings are cell well bias lines.
 11. The device according to claim 10,wherein the plurality of transistors which are arranged adjacent to oneof the plurality of bit lines and one of the plurality of cell well biaslines, connected to the plurality of bit lines and each having the wordline as a gate thereof are memory cell transistors.
 12. The deviceaccording to claim 8, wherein the first wiring is a block selectionline, the plurality of second wirings are bit lines and the plurality ofthird wirings are cell well bias lines.
 13. The device according toclaim 12, wherein the plurality of transistors which are arrangedadjacent to one of the plurality of bit lines and one of the pluralityof cell well bias lines, connected to the above bit line and having theblock selection line as a gate thereof are block selection transistors.